exploration: walking

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Walking

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letzte Änderung: 30.5.2003
Name: Walking

Instructions

  1. In this multi-faceted exploration, some facts and connections of the kinetics of walking become understandable and tangible. In the individual parts and in the details, some elementary biomechanical relationships are explained that are helpful in understanding walking.
  2. Walking has many variable parameters that can be varied to a certain extent without losing its function. If some of the parameters are varied greatly, certain variables escalate and walking becomes, for example, unphysiologically stressful for the joints, too slow and too strenuous.
    1. Angle of inclination of the pelvis against the vertical and possible movement of the pelvis (degree of flexion, forward stride).
      Tilt the pelvis forwards more or less (upwards) when walking and observe the changes. This initial exploration should above all make it possible to experience the progressive and equal (the more, the more) easing of the effort when taking powerful steps, which results from the pelvis being tilted slightly forwards. At the same time, the extent of this tilt naturally changes the work and also the perception of the back muscles: it becomes more strenuous and they tire more quickly. If the pelvis is tilted significantly forwards, the back muscles very quickly develop a cramp-like, overstrained sensation when the upper body is held upright. If the upper body is also tilted significantly forwards, the centre of gravity shifts so that the foot has to be placed forward earlier for the step, and the perceived exertion increases again, but the cramp-like sensation largely disappears. Instead, the hip extensors are noticeably activated to hold the pelvis with the upper body. Next, try to tilt the pelvis forwards or backwards with each step. Tilting in the same direction as the hip flexors pull is much easier than in the opposite direction.
    2. Lifting angle of the thigh forwards and upwards when stepping forwards and timing of the lift. Experiment with the height by which the leg pulled forwards is lifted and the time at which this begins, as well as the speed. The lifting angle depends largely on the strength of the hip flexors. If these are used forcefully, the pelvis tilts forwards slightly due to the acceleration caused by the inertia. This movement also inhibits the forward shift of the centre of gravityif all other parameters remain the same. The rectus femoris in particular will fatigue prematurely as a result. When walking, the body ’s centre of gravity typically describes a sinusoidal function as a rough approximation. Excessive lifting of the leg increases the curvature of this centre of gravity function, the gait becomes more strenuous because greater acceleration and deceleration are required here and there, and wear and tear, particularly of the joints, also increases. If the leg pulled forwards is lifted too late, there is a feeling of falling into the next step. This feeling increases if the pelvis is also tilted forwards. If the leg is lifted early and excessively, the forward movement tends to be reduced; if the leg is lifted late and far, there is a feeling of ‚falling‘ into the next step, the centre of gravity curveshows a greater amplitude, efficiency decreases and wear and tear increases.
    3. Extension angle in the knee joint when stepping forwards and possibly holding the extension.
      The gait inevitably involves an extension movement in the knee joint when the leg is pulled forwards. Without this extension, the stride length would be shortened uneconomically and the posterior cruciate ligament would be unnecessarily strained to prevent the gravity-induced ventral translational inclination of the thigh in relation to the lower leg. This extension can be reduced or excessive. If increased, additional effort that is not conducive to locomotion is exerted and felt in the quadriceps; the longer the leg is held or the slower it is extended, the more effort is exerted, particularly in the rectus femoris. Here too, the centre of gravity curveis deformed. In extreme cases, this creates the feeling of performing an eka pada prasarita tadasana with every step. If the extension of the knee joint is reduced while the action of the back leg remains unchanged, this tends to result in reduced speed, a slightly „out-of-round“ gait, greater strain on the quadriceps as the knee extensor and greater stress on the structures of the knee joint, especially the posterior cruciate ligament.
    4. Extension of the foot when stepping forwards.
      The extension movement in the ankle before the foot touches down has a major effect on the rolling behaviour of the foot. From a certain stride length and, depending on this, a certain extension in the ankle joint, a rolling movement is no longer possible. The foot must then be placed on the ball of the foot at the front and rolled from front to back before the normal rolling movement from back to front can take place. However, this can also fail to occur, so that the foot remains fully planted until it is lifted for the step forwards. This delays the stride sequence and leads to an uneven gait. In the latter case, the triceps surae from the gastrocnemius and soleus no longer actively contribute to propulsion, which further increases the loss of propulsion and places greater demands on the hip flexors to pull the leg forwards because the triceps surae are not pushing it forward a little. The less the triceps surae works, the more the hip flexors have to work to prevent the tip of the foot from bumping and tripping.
    5. Foot touchdown point and rolling movement (uni-/bidirectional).
      This parameter is closely linked to the previous one. The touchdown point depends heavily on the extension of the ankle and the stride length. The further forwards the touchdown point is, the closer the need for an inverse rolling movement from front to back before the actual movement from back to front can take place. As already discussed, this can have a major impact on the work of the triceps surae or its ability to contribute to propulsion. In the case of an inverse rolling movement before the usual one, it must also contract eccentrically before it can contribute to propulsion by contracting concentrically. Less so when walking, but when running this would increase the risk of a pulled muscle.
    6. Bending movement/springing in the knee after the foot is placed on the ground and before it is lifted.
      This movement is accompanied by a lifting and lowering of the pelvis and the rest of the body. When lowering the pelvis, the quadriceps must stop this movement in an eccentric contraction and then lift the large part of the body weight again with a concentric contraction. This causes a lot of work and effort in the quadriceps. The muscles of the lower leg are also involved to a greater extent because a greater kinetic force has to be controlled when stopping the large partial body weight. The hip muscles are also more strongly involved in stabilising during the stop. In addition, the hip extensors are activated when decelerating the lowering and lifting of the partial body weight, which would hardly be necessary without lowering the pelvis; they would only need to make their contribution to propulsion. This happens because the inertia of the partial body weight with the upper body wants to cause further hip flexion. This exploration shows one of the best ways to significantly increase the amplitude of the centre of gravity functionwithout significantly worsening the smoothness measure, which would presumably also worsen the relationship between training effect and tendency to side effects.
    7. Use of foot lifts when lifting the foot from the ground.
      The angle of plantar flexion when lifting the leg to pull it forwards determines whether we trip over our feet or not. Excessive use would place unnecessary strain on the foot lifter group and possibly cause premature fatigue. Unlike in the case of the gastrocnemius as an extensor of the ankle joint, the foot lifters are completely decoupled from the movement in the knee joint. There is no analogy to the dorsal gastrocnemius, which flexes the knee joint and extends the ankle towards the plantar side, in the ventral lower leg: none of the dorsiflexors of the ankle have an effect on the knee joint. The position of the thigh is therefore only linked to the foot lifts via the geometry, in that it makes the lower leg steeper with little or late use of the hip flexors, resulting in an increased tendency to stumble or flatter, so that it is hardly possible to strike the foot. Hip flexion and the use of the foot lifts therefore jointly determine how great the tendency to stumble is. People with weak foot lifts therefore have to lift their leg more with their hip flexors to avoid stumbling, which leads to a characteristic gait pattern.
    8. Angle of plantar flexion when the foot touches down.
      This angle is a decisive factor in the calf muscles‘ contribution to propulsion. A negative angle, i.e. dorsiflexion, and even very small angles can lead to a very hard heel strike. On the other hand, the greater the plantar flexion, the less the triceps surae can contribute to propulsion, unless an inverse rolling movement (from front to back) occurs first. The dependency described above also applies regardless of how hard the triceps surae works: its total work is ultimately an integral of the force exerted over the angular range, so the smaller the angle with otherwise the same application of force, the smaller the total force exerted must be. However, this does not rule out the possibility that the triceps surae only stretches with low force in the ankle joint and that the forward movement of the leg is exclusively or largely due to the strength of the hip flexors.
    9. Strength and radius of plantar flexion to push the body forwards.
      As already described above, the angular range is an important variable in the development of force, the other is the force applied over this path. With the same force developed at each degree, the greater the radian measure, the greater the overall acceleration of the heel and therefore of the leg. Depending on how the plantar flexion relates to the forward movement of the leg from the force of the hip flex ors and the change in the flexion angle in the knee joint, the plantar flexion can push the rest of the body upwards, push it forwards or even push the knee joint into further flexion if the quadriceps would allow this or even if the knee flexors or hip flexors would contribute to it.
    10. Stride length.
      Stride length is an important factor in the achievable stride speed and in economy. If the stride length is too short, an excessive number of steps are required for locomotion and therefore also an excessive number of reversals of movement of the leg limb, i.e. many positive and negative accelerations. Even if the individual energy required for this is less than with longer stride lengths, the total can still be significantly greater. The logic behind this is similar to the question of the speed at which you stay driest in the rain: the lower the speed, the wetter you get. At the limit, you would get infinitely wet at zero speed. A long stride length necessarily lowers the body’s centre of gravity in between. Idealised, this can be imagined as an isosceles triangle whose height decreases as the width increases. The legs of the triangle are the legs, the width of the triangle is the stride length. If the legs are largely stretched again in between, the resulting height difference has to be worked out with each step, i.e. the lost potential energy has to be added again. If, in order to avoid this, you walk with your legs bent significantly and try to keep your centre of gravity largely level, the quadriceps and hip extensors have to do a lot of variable holding work. At the limit value with maximum knee flexion, this would be the infamous duck walk, which we naturally do not try out because of its knee joint-damaging effect. This type of walking must necessarily be more strenuous than necessary. In both of the above cases, the extra work of the quadriceps and hip extensors should be clearly noticeable. Depending on the other parameters, there may be a significant stretch in the gastrocnemius of the rear leg if the triceps surae is not actively used for propulsion.
    11. Force used by the hip extensor pomus muscles/ischiocruralgroup to propel the body forwards.
      As described in the details, propulsion during walking comes mainly from the hip extensors. The greater the force used, the greater the effect on the horizontal oscillation of the pelvis and the tendency to tilt around the line between the acetabuli. Depending on how the other parameters of gait are selected, a one-sided „thrust-orientated“ gait pattern can develop, which shows a significantly increased speed in the middle range of hip extension, and a decreased speed in the time interval until the next hip extension can be performed powerfully again. This gait is basically not optimal and leads to premature exhaustion, but it takes a little longer than with other parameters, as the hip extensors are generally a rather powerful and enduring muscle group.
    12. Supination/pronation.
      When the lower leg muscles are at rest, the ankle has an inversion tendency, i.e. it will move into adduction, plantar flexion and supination without external influence, as shown in the corresponding exploration. As the triceps surae also has a slight supination effect, activity of the lower leg muscles is required to guarantee stable, balanced rolling of the foot. Individual gait patterns often show a supinationor pronation tendency, which can usually also be recognised in the wear pattern of the footwear. In principle, however, it is possible to consciously perform pronationand supination movementswhile rolling.
    13. Rotated or unrotated position of the foot at touchdown
      This part experiments with the rotation of the leg in the hip joint at the moment the foot touches the ground for the next step. Normally, the foot rolls from back to front with a movement that is not completely straight, but it is also possible to let the rolling movement run diagonally: from back-outwards to front-inwards or from back-inwards to front-outwards. In principle, both variants are not particularly compatible, especially for the knee joint, because it is not loaded axially. The variant from backwards-inwards to forwards-outwards should not occur naturally, as the leg has to be turned inwards. However, both the hip flexors, which pull the leg forwards, cause an exorotation moment in the hip joint, as does the hip extensor gluteus maximus, which was previously used primarily for more powerful steps. On the other hand, inward-rotating muscles are only found in the dorsal hip muscles and, of all the adductor muscles, only in the form of the adductor magnus, which results in a clear preponderance of the outward-rotating muscles. If you now experiment with the rolling movement from back-in to front-out and turn the leg in before the heel touches down, you will notice that this requires an unusual use of strength. The rolling movement will also appear unfamiliar and may be intuitively perceived as „wrong“. The reverse rolling movement from back-out to front-in can occur quite naturally, especially if the tone of the muscles exorotating in the hip joint is increased and a tighter gait is also used. Even with this gait, however, the subject may have doubts as to whether this movement is „correct“. Apart from this, both rolling movements impair the powerful use of the triceps surae.
    14. Rotational movement on the foot during the stride.
      This section again experiments with a movement that is not particularly physiological, especially for the knee joint and, to a lesser extent, for the hip joint. The foot can rotate both on the heel and on the ball of the foot if an inverse rolling movement from front to back takes place before the regular rolling movement. The direction of rotation can also be from a turned-in state to a turned-out state or vice versa. Here too, the experiment will show that exorotation during the step being performed is easier than final rotation. This is all the more true the greater the friction provided by the foot in place. The reason for this is the already discussed imbalance between the two groups of rotators. These rolling variants are unphysiological, among other things, because the friction on the ground creates a rotational moment in the flexed knee joint of the foot that has just been placed on the ground, based on the fact that this movement is initiated in the hip joint and occurs against the friction of the foot on the ground. Due to the flexion of the knee joint during the stride, this cannot be absorbed by the collateral ligaments, and even that would not exactly be physiological. Furthermore, the hip joint rotates unnecessarily with every step, which would also promote wear there. If the rotational movement is performed with the ball of the foot on the ground, the structures of the foot and ankle are also stressed.
    15. Lateral position of the knees in relation to the feet.
      It is another unphysiological way of walking if the knee is lateral or medial to the sagittal plane through the acetabulum and ankle joint at the moment the foot (i.e. the heel without inverse rolling movement) touches the ground, i.e. too far outwards or inwards in relation to the vertical plane through the hip joint and ankle joint. Depending on stride length and walking speed, the rolling movement typically takes less than a second. During this time, the knee would have to be brought back into the described plane in a defined manner. However, as there is only a short amount of time available, it must be accelerated there and then stopped again, i.e. negatively accelerated. It is almost impossible to fine-tune this in the short time available. Therefore, in practice, a damped oscillation around the desired position will occur during the test. If the knee is further lateral, but the foot is correctly placed in the target area, it follows that there must be both abduction and exorotation in the hip joint.
    16. Exorotation and re-rotation of the leg when stepping forwards.
      As already described, the pull of the hip flexors leads to an exorotationmoment in the hip joint. If this is not counteracted, the leg accelerated forwards would turn out. In order to place the foot back on the ground in the correct axis, the leg would have to be rotated back into the hip joint before the foot touches the ground. Here, too, the unaccustomed work of turning the leg in becomes noticeable again
    17. Raising/lowering the hip of the unloaded leg.
      This part again looks a little artificial and unnatural. However, if the gluteus medius or even more so the gluteus minimus is damaged, a pathological lowering of the hip of the free leg occurs if one or both of the muscles mentioned do not work sufficiently as a pelvic-stabilising abductor. This becomes visible in the positive Duchenne sign or Trendelenburg sign and is referred to as a waddling gait. This sinking of the pelvis requires greater hip flexion so that the foot does not drag on the floor with the toes when stepping forwards, or at least greater work by the foot lifters. A pelvic position in which both hips are at the same height is only re-established in the loading phase of the leg when its extension pushes the relevant hip upwards. If this occurs unilaterally, the result is a very unround, asymmetrical gait pattern. The joints on the contralateral (to the diseased) side are then exposed to constant small impact loads, which promotes wear and tear. Of course, this also applies to bilateral diseases. Conversely, the hip of the leg to be pulled forwards can also be lifted on a trial basis, which makes the work of the two muscles mentioned noticeable. Care must be taken to ensure that the lift is not performed from a sideways movement of the upper body via the muscles between the torso and pelvis. The strong oblique abdominal muscles would be particularly suitable for this, as would the quadratus lumborum. The trunk should be changed as little as possible, apart from an unavoidable lateral flexion of the lumbar spine. In the analysis, this naturally results in constantly changing abduction/adduction ratios of both legs.
    18. Rotational movement of the pelvis in the plane.
      Normally, the pelvis moves forwards relatively evenly when walking, apart from the small tilting and rotating movements described above, which increase with the force used and the speed achieved when walking. This rotational movement can now also be deliberately driven beyond the natural level. This results in a constant rotation of the pelvis, alternating in both directions, similar to the restlessness of a mechanical watch. This movement is of course mainly initiated by the rotationally active muscles in the hip joint. The obvious case here is that the pelvis is moved forwards on the side contralateral to the supporting leg, as also occurs naturally in the spectrum of action of the gluteus maximus. In principle, this would increase the stride width by the difference between the positions of the hip joints in the longitudinal direction. Some people may have tried this out playfully as a child. The opposite movement, i.e. moving the contralateral hip backwards, is much more difficult as it runs counter to one dimension of the activity of the gluteus maximus, and again shows that endorotation in the hip joint is a weaker movement in humans than exorotation. It doesn’t take much imagination to visualise how millions of years ago our bipedal hominid predecessors initiated a sideways escape by turning the pelvis away from the supporting leg instead of the opposite movement, turning backwards, which increases the risk of tripping over a leg.
    19. Circumduction.
      Circumduction often occurs as a result of apoplectic neurological damage in which flexion in the hip joint is lost. Instead, the affected hip is lifted so that the foot lifts off the ground, then the leg is abducted and moved forwards in an arching motion. The restricted mobility of the hip flexors can be helpful here: if the pelvis is tilted backwards at the top, this results in an impulse that accelerates the leg forwards.
    20. Average height of the pelvis.
      This topic has already been touched on previously. The centre of gravity curve can be at different levels; an above-average height presupposes excessive activity of the triceps surae, which is mainly converted into the height of the pelvis and not primarily into propulsion. If the centre of gravity curve is below average, this means that the knee joint is permanently bent further than necessary, which places considerable demands on the quadriceps and also changes the angles in the ankles, e.g. more pronounced dorsiflexion in the rear foot.
    21. Swinging the arms.
      A synchronous and counter-rotating movement of the arms serves to balance mass, reduces energy losses and thus improves economy, minimises wear and tear, especially in the knee and hip joints, and increases the possible speed of both walking and running. Without counterbalanced movement of the arms, the rotational movements of the pelvis that occur during acceleration and deceleration of the leg due to inertia would lead to a loss of strength and energy in the leg-hip joint apparatus on the one hand, and on the other hand they would be transmitted via the pelvis via the upper body to the shoulder area and head, so that counter-movements would be required there with every step. The synchronous, opposing movement of the extremity generates moments and impulses at the other end of the trunk that counteract the moments and impulses generated in the lower extremity, neutralising each other within the trunk so that its torsion and the necessary compensatory movements are much less. This is already a clearly perceptible effect when walking. The attempt to keep the arms motionless in the sense of rigid immediately leads to an unfamiliar and strained gait. If, on the other hand, the arms are relaxed, at least a kind of „passive mass equalisation“ occurs. However, for a fast, efficient and low-wear gait, the arms must be actively moved in the opposite direction to the legs. This becomes even clearer when running. The above-mentioned attempts to keep the arms rigid or only passively moving quickly render this form of movement absurd. Furthermore, this becomes even clearer with sprinters: on the one hand, they must have a lot of moving mass for a good mass balance, i.e. have voluminous arms, and on the other hand, the muscles must be able to accelerate the arm quickly, i.e. have a high muscular capacity.
    22. Rotation of the upper body.
      As argued above, the positive and negative acceleration of each leg generates an impulse via the mass inertia that accelerates the pelvis backwards or forwards, i.e. rotates it horizontally. This oscillating pelvic movement can be artificially forced. This is then mainly initiated with the rotators of the hip joint. Depending on the intensity of the movement of the arms in opposite directions, this can lead to a greater or lesser degree of rotation in the upper body.
    23. Direction: forwards – backwards.
      The forward movement of humans is deeply rooted in their ancestral tree. Many features can be found that make walking backwards much more difficult and considerably more restricted. A first self-experiment quickly makes this clear. Firstly, the propulsion provided by the triceps surae when walking and running is missing: when walking backwards, the forefoot must be touched down and rolled backwards towards the heel. As the foot must be placed on the ground with the knee joint flexed so that propulsion can then be achieved by extending the knee joint, the lower leg is relatively flat, depending on the desired speed, so that significant dorsiflexion ability is required in the ankle joint. Only with long stride lengths and speeds can a little plantar flexion still take place after the rolling movement and thus propulsion from the triceps surae be achieved. However, the ROM of the triceps surae is significantly lower here and also takes place in the upper range of the sarcomere lengths, which significantly limits the possible work and power development. Furthermore, the powerful group of hip extensors is not available for propulsion; instead, this must be provided primarily by the quadriceps, which generally prove to be significantly weaker in this respect than the hip extensors as a whole. The quadriceps can be supported by the hip flexors. These consist mainly of the iliopsoas, which has to cover a large ROM due to its long lever arm and therefore fatigues quickly. The second important hip flexor is the rectus femoris. As – with the exception of long stride lengths – the foot is lifted from the heel at the end of the rolling movement instead of from the ball of the foot, the stabilising work of the lower leg muscles is significantly more limited and must take place almost impulsively at the beginning of the rolling phase. In addition, a lot of flexibility is required in the hip flexors in order to place a foot backwards for the next step without tilting the pelvis significantly forwards. Finally, the lack of rearward vision is also a problem, which can of course be compensated for technically.

details

  1. In principle, the exploration should be carried out with the muscles warmed up throughout the body, as some muscle groups and some joints can be strained far beyond the usual level. That said, not everyone will want to carry out these explorations with the same intensity or extensively in terms of the movements, possibly because they want to protect their musculoskeletal system or this is known to be necessary, or the unaccustomed strain is difficult to assess. If performed intensively, outsiders may well get the impression that you are a member of Monty Python’s Ministry of Silly Walks or are practising for a job application there.
  2. Pelvic tilt angle.
    The angle of inclination of the pelvis has many effects: the flatter the pelvis is, the less flexibility is required in the hip flexors. People with significant mobility restrictions in this area would therefore tend to tilt their pelvis forwards to a greater or lesser extent, especially with long stride lengths. The forward tilt of the pelvis also means that the working range of all the muscles involved, both the hip flexors and the hip extensors, is more favourable because the sarcomere lengths are more favourable in terms of the force-length function and therefore more force is available, which improves economy in the lower limb and hip muscles. In the case of the rectus femoris, the anteriorly tilted pelvis would mean both a more favourable average sarcomere length (in relation to the working range of the muscle in this movement) and therefore more force during hip flexion and extension of the knee joint and, particularly in the case of mobility restrictions in this muscle, a lower sensation of stretching or tension in the respective rear leg.
  3. Effect of the legs on the pelvis.
    In addition, the inclination of the pelvis also depends on the movement of the legs: With each step, the hip-flexing torque causes a small forward tilt of the pelvis at the top due to the inertia of the leg accelerating from back to front, i.e. more flexion in both hip joints. When stepping backwards, the more forcefully the gluteus maximus pulls the iliac crest backwards. The effect of the biarticular hip extensors in the hamstrings, which work almost exclusively when only a small amount of force is applied, i.e. during a leisurely gait, is significantly smaller and opposite: as their origin is distal to the acetabuli, they do not counteract hip flexion, but rather maintain it. The rectus femoris pulls the hip joint into flexion through the force with which the knee joint is extended when walking forwards. The action of the hip flexors of the leg pulled forwards therefore tilts the pelvis more or less forwards at the top, as just described. This has an effect on the contralateral leg as well as on the upper body, as the latter has to partially absorb this through the abdominal muscles.
  4. Centre of gravity.
    As already explained, the body’s centre of grav ity typically describes a sinusoidal function to a rough approximation when walking and running. Instead of the movement of the body’s centre of gravity, which is difficult to measure empirically, the movement of the crown of the head can be considered as an approximation. This movement can be more or less ‚round‘ or ’smooth‘. Smooth can actually be understood as the mathematical measure of smoothness, for example in the form of an integral of the second partial derivatives, but the intuitive concept of smooth also does sufficient justice to this. A curve that is as smooth as possible has a certain connection with economical and low-wear running. However, this does not mean that a powerful emphasis on certain aspects of the motion sequence would necessarily lead to a less smooth curve. Nor does a smooth curve necessarily result in a movement that minimises wear. The situation is too complex for such conclusions and too many individual factors can be compensated for by a single other or a number of others. Apart from these considerations, the function of the body’s centre of gravity in running and walking differs in such a way that when running, the body’s centre of gravity is at its highest in the middle of the flight phase, i.e. when the feet are at maximum distance. In walking, however, the body’s centre of gravity is at its lowest when the feet are at maximum distance from each other instead of at its highest as in running. This also means that when walking, part of the kinetic energy from one step to the next is stored or converted into potential energy, whereas when running with the opposite centre of gravity behaviour, the storage of kinetic energy tends to be in the form of elastic energy in the muscle-tendon system. Incidentally, a runner with a good running style will have a recognisably lower vertical amplitude in their centre of gravity function than when walking.
  5. Horizontal oscillation of the pelvis.
    In analogy to the fact that hip flexion tends to tilt the pelvis forwards at the top (on both sides) when a leg is pulled forwards, the hip-extending action of the gluteus maximus during forced gait has the effect of tilting the pelvis backwards at the top, which brings the autochthonous back muscles into action. In addition to the movement of the pelvis around its transverse axis just described, i.e. the axis through the acetabuli, the inertia of the leg pulled forwards at the beginning of this phase causes this side of the pelvis to move backwards, whereas the inertia of the same leg at the end of this phase pulls the pelvis slightly forwards, resulting in a periodic oscillation of the pelvis around its vertical axis. This movement must also be absorbed by the hip and leg muscles, especially the powerful rotatory muscles in the hip joint, adductor magnus as the most important end rotator and gluteus maximus as the most important exorotator, but also the dorsal hip muscles. In addition, rotationally active muscles of the lower trunk are also involved, in particular the autochthonous back muscles and the oblique abdominal muscles. The effect on the abdominal muscles is probably familiar to many beginners of running in the form of sore muscles.
  6. Propulsion.
    Propulsion during walking comes mainly from the hip extensors, because they are the main ones that move the pelvis and thus the body’s centre of gravity forward in relation to the foot on the ground. This is the biarticular part of the hamstrings on the one hand and the gluteus maximus on the other, with very little coming from the dorsal hip muscles. This work can be carried out with very different levels of force, on the one hand rather lightly, so that only the existing momentum, i.e. the kinetic energy, is maintained, and on the other hand so powerfully that a pronounced thrust is generated. Of course, the total acceleration that the hip extensors can achieve in total depends on the ROM of the movement and therefore ultimately also on the application time and muscle performance. Furthermore, the triceps surae can contribute to propulsion to a certain extent by pushing the ankle forwards during the stride. This can also be done with very variable force: if there is no extension of the ankle due to the force of the triceps surae, the entire sole of the foot can remain on the ground until the leg is pulled forwards by the hip flexors or, in the case of long strides, until the restriction of mobility in the ankle joint in the direction of dorsiflexion causes the heel to lift off. This means that two impulses are possible with every step: one from the hip extensors and one from the triceps surae. With intensive use, this can result in a slightly out-of-round gait pattern or a significantly fluctuating speed function.
  7. The musculoskeletal system of the lower limb has an interesting anatomical structure. Adapted to the requirements of bipedal forward movement, there are powerful muscles that stretch in the ankle joint to push the body forwards, but also cause plantar flexion, which has to be cancelled out again so that the same movement can be repeated with the next step. This is what the foot lifter group does. However, they do not have to and cannot make an active contribution to propulsion, which means that they are much less powerful. At the same time, for this very reason, none of them need a connection to the thigh; they only have to lift the forefoot periodically when running and walking. The other muscles that provide propulsion are the gluteus maximus and hamstrings. In the latter, the muscles act as simultaneous knee flexors and hip extensors. The advantage of this is that the counter movement takes place in both neighbouring joints, i.e. in the hip joint and knee joint, both when stepping forwards and when pushing off the rear foot. In order for this to be supported at all by these muscles, the lever arms and therefore the arc dimensions travelled must be different in the two joints. In fact, the lever arm in the knee joint is significantly smaller – also due to the size of the joint compared to the hip joint. This fact has important implications for stretching the muscles. If, for example, the rectus femoris is to be stretched, the movement in the hip joint per degree of angle is more important than that in the knee joint. This also explains the good effectiveness of the 2nd quadriceps stretch on the wall, which stretches from a widely flexed position in the knee joint for increasing stretching, but extends in the hip joint.
  8. Running vs. walking.
    Some of the statements made about walking apply unchanged or even more so to running, whether in the form of more leisurely jogging with shorter stride lengths, moderate exertion and the specific feature that speech remains possible in largely unchanged form due to the moderate oxygen requirement and therefore limited respiratory excursion and frequency, orrunning, which achieves a higher metabolic level with a higher level of effort and longer stride length, significantly more pronounced use of the gluteus maximus and the hamstrings as the muscle groups that mainly provide propulsion, which results in such an increased oxygen demand in the tissues that a very significantly increased breathing frequency and depth is achieved, in which speech no longer functions effortlessly and continuously. However, there are some clear differences between walking and running. For example, unlike walking, in which the stance legand free leg phases of each leg follow each other seamlessly, jogging and running have a flight phase in between, which significantly changes some parameters. The acceleration of the extremities in running is significantly higher than in walking or jogging, as a result of the stride frequency and length. As a result, significantly more power has to be developed against the mass inertia. As a reminder: in acceleration, time is in the denominator compared to speed, just as it is in power compared to work, so the quotient increases hyperbolically with decreasing time. In addition, the mass balance between the lower and upper extremities becomes much more important when running. Without the synchronised counter-rotating movement of the upper limb, the acceleration and deceleration of each leg would result in a large torsion of the trunk (or rotation in space), which would have to be exactly reversed in the next step, which many muscles of the trunk could hardly do in the long term, and which would also mean a massive loss of energy and speed. The higher the mass of the upper limb, the better this mass balance works, with mass being a proportional factor. In addition to the mass, the amplitude of the movement of the upper limb also plays a very important role, as this is a movement in time, it is included in the calculation hyperbolically, meaning that the required muscle power increases non-linearly. This is the reason for the significantly different stature of, for example, a long-distance runner and a sprinter. The latter not only needs a high-mass upper limb, as argued above, but also the corresponding performance of the frontal abductors and their antagonists or retroverters. The shoulder muscles will therefore always be well developed in sprinters, who cannot manage without appropriate strength training. Marathon runners, on the other hand, tend to be minimalists when it comes to the upper body, as their speed, which is about half as fast, requires disproportionately less muscular performance.
  9. This exploration also serves to give the teacher a greater sensitivity to abnormalities in the gait of their pupils and, based on a certain understanding of the correlations, to be able to search for possible causes and possibly treat them.